// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using System.Collections.Generic;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;

namespace TLens.Analyzers
{
    sealed class DuplicatedCodeAnalyzer : Analyzer
    {
        readonly Dictionary<string, List<MethodDefinition>> strings = new Dictionary<string, List<MethodDefinition>>();

        protected override void ProcessMethod(MethodDefinition method)
        {
            // TODO: Add more cases to detect potencial code duplications
            foreach (var instr in method.Body.Instructions)
            {
                switch (instr.OpCode.Code)
                {
                    case Code.Ldstr:
                        var str = (string)instr.Operand;

                        // Short strings are hard to identify as true duplicates
                        if (str.Length < 3)
                            continue;

                        // It'd common to throw exception referencing parameter name
                        if (method.HasParameters && method.Parameters.Any(l => l.Name == str))
                            continue;

                        if (!strings.TryGetValue(str, out List<MethodDefinition> existing))
                        {
                            existing = new List<MethodDefinition>();
                            strings.Add(str, existing);
                        }

                        if (!existing.Contains(method))
                            existing.Add(method);

                        break;
                }
            }
        }

        public override void PrintResults(int maxCount)
        {
            var entries = strings.Where(l => l.Value.Count > 1).OrderByDescending(l => l.Value.Count).Take(maxCount);
            if (!entries.Any())
                return;

            PrintHeader("Possibly duplicated logic in strings handling");
            foreach (var entry in entries)
            {
                Console.WriteLine($"String value \"{entry.Key}\"");
                foreach (var m in entry.Value)
                    Console.WriteLine($"\tMethod '{m.ToDisplay()}'");
                Console.WriteLine();
            }
        }
    }
}
